How much is this additional head flow worth? Cost benefit Analysis
01-19-2007, 05:03 PM
#1
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How much is this additional head flow worth? Cost benefit Analysis I trying to determine the benefit to some additional flow which I can get on my heads by additional porting. This is based upon the collected data of a CNC head porter. What I have is a table with valve lift, and then three CNC options which I have. The range of values for CNC#1 represents the increase in intake air flow which would be acquired if I chose CNC#2 over CNC#1. CNC#2 represents the increase in airflow which would be acquired if I chose CNC#3 over CNC#2. CNC#3 is filled with zeros because it represents the highest flowing capability which the CNC porter offerers (ie. there is nothing better to upgrade too). If that doesn't make sense then this should help: For .100" valve lift, if I chose CNC#1 I would be leaving 2.78% flow capability "on the table" by not choosing CNC#2 and for the same valve lift choosing CNC#2 would not yield any additional air flow if I chose the CNC#3.
Lift.....CNC#1.....CNC#2.....CNC#3
............%/CFM.......%/CFM........
0.1.....2.78%/2.....0.00%/0.....0.00%
0.2.....0.00%/0.....0.00%/0.....0.00%
0.3.....0.97%/2.....0.00%/0.....0.00%
0.4.....2.34%/3.....1.16%/3.....0.00%
0.5.....4.18%/4.....2.75%/8.....0.00%
0.6.....4.25%/8.....1.59%/5.....0.00%
0.625...3.87%/7.....1.58%/5.....0.00%
COST....$370.....$770.....$1700
Now, what is the cost benefit?
//**EDIT**
Engine specs: 402cid, [Comp XER (@.006" 287/289) (@.050" 238/240) (lift .604/.609)], FAST 90/90, 85mm MAF, 92mm air box, 1 3/4 longtubes
//**EDIT*#
Lift.....CNC#1.....CNC#2.....CNC#3
............%/CFM.......%/CFM........
0.1.....2.78%/2.....0.00%/0.....0.00%
0.2.....0.00%/0.....0.00%/0.....0.00%
0.3.....0.97%/2.....0.00%/0.....0.00%
0.4.....2.34%/3.....1.16%/3.....0.00%
0.5.....4.18%/4.....2.75%/8.....0.00%
0.6.....4.25%/8.....1.59%/5.....0.00%
0.625...3.87%/7.....1.58%/5.....0.00%
COST....$370.....$770.....$1700
Now, what is the cost benefit?
//**EDIT**
Engine specs: 402cid, [Comp XER (@.006" 287/289) (@.050" 238/240) (lift .604/.609)], FAST 90/90, 85mm MAF, 92mm air box, 1 3/4 longtubes
//**EDIT*#
Last edited by squealingtires; 01-19-2007 at 06:11 PM.
01-19-2007, 05:37 PM
#2
Flow increases at .300-.400" are going to make the biggest difference in performance (if you're running an LS6 or FAST intake). Flow differences at .500" will help some, but flow increases above that will not gain you much if anything. I know from personal experience. Mid-lift flow is where it's at when running the LS6 or FAST intake. If you're running a ported single plane or sheet metal intake, then all the lift improvements help. But honestly, a 2.34% gain at .400" is 6 cfm. That's going to be worth no more than 10 rwhp so use that as your value/hp gain figure.
__________________
2013 Corvette Grand Sport A6 LME forged 416, Greg Good ported TFS 255 LS3 heads, 222/242 .629"/.604" 121LSA Pat G blower cam, ARH 1 7/8" headers, ESC Novi 1500 Supercharger w/8 rib direct drive conversion, 747rwhp/709rwtq on 93 octane, 801rwhp/735rwtq on race fuel, 10.1 @ 147.25mph 1/4 mile, 174.7mph Half Mile.
2016 Corvette Z51 M7 Magnuson Heartbeat 2300 supercharger, TSP LT headers, Pat G tuned, 667rwhp, 662rwtq, 191mph TX Mile.
2009.5 Pontiac G8 GT 6.0L, A6, AFR 230v2 heads. 506rwhp/442rwtq. 11.413 @ 121.29mph 1/4 mile, 168.7mph TX Mile
2000 Pewter Ram Air Trans Am M6 heads/cam 508 rwhp/445 rwtq SAE, 183.092 TX Mile
2018 Cadillac Escalade 6.2L A10 Pat G tuned.
LS1,LS2,LS3,LS7,LT1 Custom Camshaft Specialist For custom camshaft help press here.
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2013 Corvette Grand Sport A6 LME forged 416, Greg Good ported TFS 255 LS3 heads, 222/242 .629"/.604" 121LSA Pat G blower cam, ARH 1 7/8" headers, ESC Novi 1500 Supercharger w/8 rib direct drive conversion, 747rwhp/709rwtq on 93 octane, 801rwhp/735rwtq on race fuel, 10.1 @ 147.25mph 1/4 mile, 174.7mph Half Mile.
2016 Corvette Z51 M7 Magnuson Heartbeat 2300 supercharger, TSP LT headers, Pat G tuned, 667rwhp, 662rwtq, 191mph TX Mile.
2009.5 Pontiac G8 GT 6.0L, A6, AFR 230v2 heads. 506rwhp/442rwtq. 11.413 @ 121.29mph 1/4 mile, 168.7mph TX Mile
2000 Pewter Ram Air Trans Am M6 heads/cam 508 rwhp/445 rwtq SAE, 183.092 TX Mile
2018 Cadillac Escalade 6.2L A10 Pat G tuned.
LS1,LS2,LS3,LS7,LT1 Custom Camshaft Specialist For custom camshaft help press here.
Custom LSX tuning in person or via email press here.
01-19-2007, 06:09 PM
#3
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I made some changes to the original post by converting the %'s to actual airflow values in CFM units according the the flow testing performed at 28" of H2O. I also added engine specs.
How do you see each CNC option affecting low, mid, and high RPM performance?
How do you see each CNC option affecting low, mid, and high RPM performance?
01-19-2007, 07:01 PM
#4
Id say #1 is the best bang for the buck. forget about #3 far as Im concerned. Id just get some aftermarket heads before I did #3. according to patrickG's 10rwhp estimate at 6cfm, your lookin at an average of maybe 8HP to go from #1 to #2? doesnt sound worth the $400 extra price tag to me.
